Higher intake of omega-6 fatty acids, primarily linoleic acid, from vegetable sources is associated with lower blood pressure in healthy adults, according to an article published online July 7 by Hypertension.

Omega-6 fatty acids, mainly linoleic acid, are polyunsaturated essential fatty acids that must be obtained from food because the body cannot make them in sufficient quantity. Omega-6 acids are plentiful in soybean, safflower, sunflower, and corn oils, as well as in tofu, nuts and seeds.

The International Study of Macro/Micro-nutrients and Blood Pressure (INTERMAP), led by Katsuyuki Miura, MD, PhD, was the first comprehensive population-based investigation on linoleic acid and blood pressure; it was also the first such study in both eastern and western populations. Researchers studied 4,680 men and women ages 40 to 59 years from the People's Republic of China, Japan, the United Kingdom and the United States.

In an analysis of a subset of 2,238 individuals called the "non-intervened" participants-adults who consumed no therapeutic diet or nutritional supplements, had never been diagnosed with cardiovascular disease, diabetes or hypertension and took no medication for those conditions---researchers found a statistically significant association between higher linoleic acid intake and lower blood pressure.

"Our findings indicate a favorable influence of linoleic acid on high blood pressure, a well-known cardiovascular disease risk factor," said Miura, associate professor in the department of health science at Shiga University of Medical Science in Shiga, Japan.

"These results lend support to current recommendations for increased ingestion of polyunsaturated fatty acids from vegetable sources, in place of saturated fatty acids from animal sources, for cardiovascular disease prevention."

Study participants provided four in-depth 24-hour dietary recall surveys, eight blood pressure measurements at four separate office visits and two 24-hour urine collections so that researchers could determine nutrient intake.

"In the non-intervened group, with control for 14 variables, we found that a higher linoleic acid consumption of about 9 grams/day was associated with a 1.4 millimeters of mercury (mm Hg) lower average systolic blood pressure and a 1.0 lower average diastolic blood pressure," Miura said.

Miura said "Lowering the systolic blood pressure of a population by 'small' amounts, such as 2 mm Hg, is estimated to reduce mortality rates by 6 percent for stroke and by 4 percent for coronary heart disease."

Vegetable oil was the main food source supplying linoleic acid in the study (49 percent of the total consumed in the People's Republic of China, 30 percent in Japan, 28 percent in the United States and 17 percent in the United Kingdom). Other significant sources included table spreads, salad dressings, vegetarian meat substitutes such as tofu, grains and flour, nuts/nut butters and breads/rolls/biscuits/related products.